Slow worm description

Being a legless lizard, the slow worm (Anguis fragilis) is often mistaken for a snake. However, there are certain features that separate the slow worm from snakes, including the presence of eyelids and ear openings (2).

This species can be locally abundant and, in Britain for instance, it is likely to be the most commonly seen reptile (3). Adults have a smooth, shiny appearance (4), and a grey or bluish belly. The male and female differ in appearance; the female is usually brown, copper-coloured or red on the back, with brown or black sides, often with lighter iridescent flecks. In many individuals there is a dark stripe passing along the middle of the back and stripes running along the sides of the body. The male varies in colour, being greyish, brown, or coppery- or reddish-brown, typically without stripes. The male usually has a broader, longer head than the female (2).

Occasionally, individuals may have blue spots, a feature that is more common among males than females. In juvenile slow worms, the back is iridescent silver, gold, bronze or copper and the sides are brown or black (2).

Related species

Slow worm biology

Although slow worms, like snakes, are often feared and persecuted, they should be welcome visitors to gardens as they feed largely on slugs, snails and other slow-moving garden pests (5).

The scientific name Anguis fragilis means 'fragile snake' (2), and refers to the ability of this lizard to shed its tail when seized; the tail may continue to wriggle after being shed, and can distract predators while the slow worm escapes (5). A new tail begins to regenerate after a couple of weeks (2). Although this species is widespread, it is rather secretive (2)

The slow worm usually emerges from hibernationin March, and courtship tends to take place between mid-May and late June, at which time males typically become aggressive towards each other (2). During courtship, a male takes hold of the female by biting her head or neck, and the bodies of the two lizards will become intertwined. Courtship may last for as long as 10 hours before copulation occurs (2).

Depending on the local climate, the female slow worm will mate annually or once every two years. The slow worm is ovoviviparous, and instead of laying eggs, the female gives birth to an average of eight live young between mid-August and mid-September. The young slow worms are initially encased in the egg membrane and measure from 70 to 100 millimetres in length. It takes between six and eight years for the slow worm to become fully grown, although the male reaches sexual maturity at three or four years of age. The female becomes sexually mature at four or five years of age (2).

This species is relatively long-lived, with one specimen known to have lived for 54 years (5). The skin of the slow worm is shed at intervals throughout its life (2).

Slow worm range

The slow worm is widely distributed throughout Britain and continental Europe, from Scandinavia south to northern Spain and Portugal. It also occurs in extreme northern Africa, eastwards to southwest Asia and western Siberia (2)(4).

Species with a similar range

Slow worm habitat

The slow worm is found in a wide range of open habitats and tends to take refuge under stones, planks of wood or sheets of corrugated iron in the sun, rather than basking. It is commonly found in gardens and compost heaps, where food is plentiful and the rotting plant material creates warm conditions (3).

Slow worm threats

Slow worm conservation

In the United Kingdom, the slow worm is protected under Schedule 5 of the Wildlife and Countryside Act (1981). Under this act, it is illegal to kill, injure, and sell individuals of this species.

The slow worm is classified as a ‘Priority Species’ under the UK Biodiversity Action Plan (UKBAP), as it is itself a declining species, as well as a good `indicator` species for a declining taxonomic group (6). The slow worm is also listed under Appendix III of the Bern Convention (7).

Authentication

Glossary

Hibernation

A winter survival strategy characteristic of some mammals in which an animal's metabolic rate slows down and a state of deep sleep is attained. Whilst hibernating, animals survive on stored reserves of fat that they have accumulated in summer.

Ovoviviparous

Ovovivipary is a method of reproduction whereby the egg shell is weakly formed and young hatch inside the female; they are nourished by their yolk sac and then ‘born’ live.

Taxonomic

Relating to taxonomy, the science of classifying organisms, grouping together animals which share common features and are thought to have a common ancestor.

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